In U.S. Pat. No. 2,830,612, there is described an anticondensation device for a flush tank in which hot water is injected into a cold water supply to the tank through a check valve and a restrictor orifice. I have experimented with this device and have found that whilst preventing condensation it leaves several problems unsolved. The form of check valve employed is very prone to chatter, resulting in a noise problem, and there is nothing to prevent hot water from entering the cold water supply in the event of a pressure drop in the latter. Furthermore, the device is not adjustable.
I am aware of the check valve structure disclosed in U.S. Pat. No. 2,044,629 to Parker in which two valve members are arranged in series, one of the valve members being movable relative to the other within a chamber forming part of the fluid path from inlet to outlet of the valve structure so as to provide a dashpot effect on opening or closing of the valve. I am also aware of U.S. Pat. No. 2,682,890 to May for a safety valve in where a piston operated by the pressure of fluid upstream of the valve acts as a lifter for the valve, and U.S. Pat. No. 2,646,066 to Nemetz for a check valve for lubrication systems in which a first valve member in the form of a piston acts as a lifter for a second ball-type valve. However, none of these valves operates or is constructed in the same manner as that now to be described, nor do they have the same purpose, which is here to provide a simple yet smoothly and silently operating adjustable check valve.